1. Field of the Invention
The present invention relates to a light emitting diode with a transparent ITO layer as an electrode layer and a method of fabricating the light emitting diode, and more particularly, to a light emitting diode with enhanced luminance and light emitting performance due to increase in efficiency of current diffusion into an ITO layer, and a method of fabricating the light emitting diode.
2. Discussion of the Background
A light emitting diode is a photoelectric conversion device having a structure in which an N-type semiconductor and a P-type semiconductor are joined together, and emits light through recombination of electrons and holes. As an example, a GaN based light emitting diode has been known as such a light emitting diode. A GaN based light emitting diode comprises light emitting cells each having an N-type semiconductor layer, an active layer (or a light emitting layer) and a P-type semiconductor layer which are made of GaN based materials and sequentially formed on a substrate made of sapphire, silicon or the like.
In general, a light emitting cell is configured in such a manner that an etching process is performed from a P-type semiconductor layer to an N-type semiconductor layer to allow a portion of the N-type semiconductor layer to be exposed to the outside, and electrode structures or electrical contact structures for current application are formed on top surfaces of the P-type semiconductor layer and the N-type semiconductor layer exposed to the outside.
Particularly, since a light emitting region through which light is emitted is formed on top of the P-type semiconductor layer, a transparent electrode layer through which the emission of light is not prevented is required. A Ni/Au layer with a superior electrical property has been employed as such a transparent electrode layer. However, since the Ni/Au layer has very low transmittance for visible light in spite of the superior electrical property, there is a problem in that the light emitting efficiency of a light emitting diode is lowered.
Therefore, there has been suggested a technology in which an ITO (Indium Tin Oxide) layer with a tunnel structure applied thereto for forming an ohmic contact is used as a transparent electrode layer on a P-type semiconductor layer instead of a Ni/Au layer. There is an advantage in that the ITO layer has an excellent transmittance of 90% or more for visible light. However, a further improvement has been required in that the ITO layer has a low electrical property as compared with the existing Ni/Au layer. Particularly, many studies for enhancing a current property between an ITO layer and a contact connection portion such as a contact pad or an end of a wiring have been conducted in the art.